Nowadays mobile cameras, such as digital cameras and mobile phone cameras are very common. The size of the mobile camera has an essential role, when the mobile camera is integrated with other mobile device, such as a mobile phone, watch, MP3-player or pocket computer. The size of the camera can be reduced by reducing the size of the camera's components, such as lens, shutter, aperture construction (sometimes combination of shutter and aperture, namely diaphragm shutter) and image sensors. The smaller the camera's component, the smaller the camera is and also smaller the end product. Also the simplicity, reliability and power consumption of the camera's components are very important factors in mobile camera devices.
It is also common to minimize number of components or limit their adjustability in order to achieve small size. These solutions are typically compromises between overall size and achieved image quality, or lead to decrease in range of usability.
The present invention addresses to develop especially the aperture constructions of the camera's components. The camera's aperture is used for controlling the amount of light that reaches the film or digital sensor. The aperture means the diameter of the lens opening. The larger the diameter of the aperture, the more light reaches the film/image sensor. Aperture is expressed by F-number so that the smaller the F-number (or f/value), the larger the lens opening (aperture).
Aperture size affects to the depth-of-field. Small aperture (high f-number, such as f/22 in FIG. 1A) increases the sharpness of distant objects, or in other words increases depth-of-field, which means more elements of a picture, from foreground to background, become sharply focused. This can create a distinct sense of depth to a photograph, drawing the viewer into the picture. It is well known that small apertures are used especially for most landscape photographs.
The effect of large aperture (small f-number, such as f/4) is illustrated in FIG. 1B. The large aperture produces shallow depth-of-field, which means the area of sharp focus in the picture will be small. It is well known that small apertures are used especially for isolating the subject of the picture while throwing the background and other distracting elements out of focus. Some useful applications of large apertures include portraits and wildlife close-ups.
Generally speaking one can say that the unfocused light will become sharper as the aperture number increases (aperture size becomes smaller).
An exploded view of a traditional prior art implementation for adjustable aperture is shown in FIG. 2. The prior art implementation comprises complex wing mechanism that needs an actuator, for example stepper motor, for operation (part count typically over 10 pcs). The wing mechanism can be operated with the actuator so that desired aperture size is achieved, as illustrated in FIGS. 2A-2D.
However, some problems relate to the prior art aperture implementations. At first they are very complex whereupon there is a risk to break down or jam. Secondly the shape of the prior art aperture is not fully circular, which can affect distortions into the picture. In addition weight and size of the prior art aperture are not easily reduced by conventional manners. Furthermore the manufacturing of the prior art aperture implementation is quite complex and time consuming because of the complexity of the aperture structure.